Method and apparatus for replacing old underground conduits

ABSTRACT

In a method and an apparatus for replacing old underground conduits ( 4 ), the old conduit ( 4 ) is first laid bare with the aid of a ground drilling device ( 8 ) with an overdrilling head and then, in turn, a new conduit ( 5 ) is drawn in with the aid of the drill rods ( 7 ) and at the same time—in a uniform operating step—the old conduit is pulled out of the ground.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of prior filed U.S. application Ser.No. 12/441,066, filed Mar. 12, 2009, the priority of which is herebyclaimed under 35 U.S.C. §120, and which is the U.S. National Stage ofInternational Application No. PCT/EP2007/007828, filed Sep. 7, 2007,which designated the United States and has been published asInternational Publication No. WO 2008/031536 and which claims thepriority of German Patent Application, Serial No. 10 2006 043 772.1,filed Sep. 13, 2006, pursuant to 35 U.S.C. 119(a)-(d).

The content of U.S. application Ser. No. 12/441,066 is incorporatedherein by reference in its entirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

The invention relates to a method of replacing old underground conduits,which involves initially laying bare the old conduit, without alteringits course in the ground, and then removal thereof from the ground anddrawing in a new conduit, and which claims the priority of German patentapplication 10 2006 043 772.1, the content of which is incorporated byreference.

Methods of this type are known; German Patent document 195 04 484 C1describes a device for removing buried cables with the aid of aring-shaped drill head moving over the cable and equipped with nozzlesfor a flushing liquid. Soil surrounding the cable or several cables iswashed away with the assistance of the nozzles to thereby expose thecable which then can be pulled out from the ground. The device has aneccentric connection for a hollow rod assembly comprised of individualrod sections connected to one another. The hollow rod assembly meets twotasks; Firstly, it supplies the device with flushing liquid, andsecondly, it propels the device between a starting pit on one hand and adestination pit on the other hand.

When the device has washed the conduit free and reached the destinationpit, the exposed cable is pulled out of the created borehole and, afterremoval of the flushing device, a connection adapter is secured to therod assembly for attachment of one or more conduits. These conduits arethen pulled into the flushing borehole with the aid of the rod assemblyin the direction of the starting pit.

A further multistage method for trenchless replacement of undergroundconduits is described in the German patent document 102 11 833 (GBpatent document 2 386 767). This device is additionally equipped with aboring bit and a further tool on its rearward end. It lays bare theburied conduit in the described manner and permits the exposed conduitto be pulled out from the flushing borehole. The old conduit can herebybe connected with a new conduit in order to be able to execute in asingle operating cycle the withdrawal of the old conduit and the pullingin of the new conduit. How and when the drill rods are removed from theflushing borehole is not described.

SUMMARY OF THE INVENTION

The invention is now based on the problem to technically simplify theafore-described method and thus to improve it with respect toconstruction as well as cost factor.

This is realized in accordance with the invention by a method of theafore-stated type in which the old conduit, after being laid bare, ispulled out and, at the same time but separately, the new conduit isdrawn in.

It is of particular advantage when the pulling of the old conduit isconcluded by a preferred continuous comminution thereof. A furthersubstantial economic advantage is realized when the old conduit and thenew conduit are pulled out of the flushing borehole by a common drive.

This may be implemented by an apparatus having a pulling drive which ismovably arranged on a mounting and acts on the flushing head rods aswell as on the old conduit. The mounting is preferably provided with aclamping apparatus and/or a guide for the old conduit and the drive isarranged on a carriage. In order to facilitate comminution of the oldconduit, a clamping apparatus is preferably located behind the drive.

In accordance with the conduit replacement according to the invention,the old conduit, after being washed free, is pulled out of the flushingborehole in a first operating step with the aid of the drive acting inthe starting pit and, at the same time, the new conduit is drawn in withthe aid of the drill rods. This is implemented in accordance with thestructure of the drill rods in single stages having a duration which isgoverned by the length of the rod members in the second stage of themethod.

The particular advantage of the method according to the invention is thefact that it has only two stages and accordingly the withdrawal of theold conduit and the installation of the new conduit is realized at thesame time, preferably with a common pulling apparatus.

BRIEF DESCRIPTION OF THE DRAWING

An exemplary embodiment of the invention will now be described ingreater detail with reference to the drawing. The drawings show in

FIG. 1 the simultaneous conduit replacement after the old conduit hasbeen washed free, and

FIG. 2 an apparatus for simultaneous pulling in of the new conduit andpulling out of the old conduit.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A channel which has been washed free in a conventional manner extendsbetween a starting pit 1 and a destination pit 2 and accommodates an oldconduit 4 and a new conduit 5 which is connected by a coupling 6 to arod assembly 7 comprised of one or more members, whereas the old conduit4 is connected directly or via an not shown intermediate piece, like therod assembly 7, to a drilling apparatus 8. The drilling apparatus 8provides propulsion of a not shown drill head, arranged on the forwardend of the rod assembly 7, for laying the conduit 4 bare as well aspulling in the new conduit 5 and pulling out the old conduit 4.

More specifically, the apparatus includes a mounting 9 on which a drive10 is movable to incrementally pull out the rod assembly 7 from theborehole 3 and at the same time to pull in the new conduit 5 via thecoupling 6 as well as to pull out the old conduit 4 from the flushingborehole.

This is realized with the aid of the common drive 10 for the rodassembly comprised of single members, on one hand, and for the oldconduit 4, on the other hand. To render this possible, the rod assembly7 and the old conduit 4 extend through a clamping apparatus 11 and thento a rod assembly connection 12 of the common drive 10 and a grabcoupling 13 for the old conduit 4. The grab coupling 13 remains closedduring rearward movement of the drive 10 and removal of a rod sectionand opens only when the clamping apparatus 11 is closed to then returnthe drive 10 from its rearward position to its not shown forwardposition and to subsequently close again. As a result, one of theclamping apparatuses 11, 13 for the conduit 4 is closed at all times.

A clamping apparatus 14 for the old conduit 4 is provided in therearward part of the mounting 9 and is placed adjacent a shear 15 bymeans of which the old conduit 4 is cut into single pieces 16 which canbe easily handled.

In summary, an apparatus is involved which is simple in structure andpermits a rapid and in particular effective replacement of one or moreold conduits with one or also more new conduits and which, compared toconventional apparatuses, eliminates an operating step, namely aseparate withdrawal of the exposed old conduit. In addition, theapparatus enables execution of all essential operating steps with asinge device.

What is claimed is:
 1. Apparatus for replacing a buried old conduit witha new conduit, comprising: a mounting; a rod assembly coupled to the newconduit; a pulling drive movably supported on the mounting andoperatively connected to the rod assembly and to the old conduit; a rodassembly connection connecting the pulling drive to the rod assembly;and a grab coupling connecting the pulling drive to the old conduit. 2.The apparatus of claim 1, further comprising two clamps in spaced apartrelationship on the mounting for releasably clamping the old conduit. 3.The apparatus of claim 1, wherein the rod assembly is comprised ofsingle interconnected rod members.
 4. The apparatus of claim 1, furthercomprising a clamp arranged in a pulling direction behind the pullingdrive, and a cutting blade placed adjacent the clamp at a side distal tothe drive to separate a part of the old conduit as the old conduit ispulled out.
 5. The apparatus of claim 1, wherein the pulling drive isoperatively connected to the rod assembly and supported on the mountingfor movement between a forward position in which the pulling drive isclamped to the old conduit for simultaneously pulling out the oldconduit and drawing in the new conduit in a same direction, and arearward position in which the pulling drive is decoupled from the oldconduit.
 6. The apparatus of claim 5, wherein the pulling out of the oldconduit and the drawing in of the new conduit are realizedsimultaneously in increments as the pulling drive shuttles between theforward and rearward positions.
 7. The apparatus of claim 1, wherein themounting extends at an incline.